Regarding your question about GPS tracking. These vehicles are equipped with OnStar and I do believe 2009 GMC Envoy is equipped with the digital version not like the old days where original first generation OnStar is no longer compatible with the system. I do not know if this answer will help you in any way unless you are law enforcement then you can contact OnStar with the legitimate reason and they can locate the vehicle via GPS included with OnStar module.
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